TT Talk: Bulk cargo storage fire risks

 

Warehouses storing bulk cargo – such as grain, coal, fertilizer, biomass and powders – face a unique combination of fire risks. Beyond conventional fire hazards, operators of these facilities must contend with the threat of dust explosions and the challenge of safely using electrical and mechanical equipment in combustible dust environments. Robust strategies for risk mitigation and operational resilience are essential.  

How dust explosions manifest

A dust explosion requires five elements – fuel (dust), oxygen, ignition source, dispersion and confinement – all of which can be present in a bulk cargo warehouse. Fine particles from bulk materials can easily become airborne and form combustible dust clouds, while electrical and handling equipment, hot works, mechanical sparks, static discharge and self-heating are all potential sources of ignition. 

Primary explosions can occur inside warehouse equipment, such as silos and conveyors, but the greatest danger is from secondary explosions, where accumulated dust is disturbed and ignited, causing rapid and widespread blast and fire damage. High-density storage, enclosed conveyors, poor ventilation, inadequate housekeeping and improper segregation of hazardous materials all increase the risks. 

Preventing dust explosions

Operators of bulk cargo warehouses should always conduct a dust hazard analysis when looking at potential new cargoes to know the explosion risks, ignition sources and mitigation strategies, and is essential for facilities handling bulk cargoes, to understand the risks associated with the cargo being handled. 

Dust can be captured at its source using properly designed, installed and maintained engineering systems, while dust explosion prevention and mitigation systems – such as pressure-relief systems and explosion-isolation devices – should be considered for bulk handling facilities and equipment. High-risk areas should be separated, and dust-tight equipment should be used to minimise dispersion.  

Settled dust on floors, surfaces and concealed spaces should be continually removed using safe cleaning methods that do not increase the explosion risk, and all equipment, cleaning equipment and infrastructure should be regularly inspected and maintained to prevent overheating, sparks and mechanical failure. Training should be carried out to ensure all staff understand the specific dust explosion hazards of the cargo being handled and know the safe cleaning procedures and equipment required to reduce dust build-up. 

Sensors and alarms should be used to detect dust concentrations and build-up, cargo temperature rises, and heat increases in high-risk areas such as bearings and motors before conditions become dangerous. Spark detection and suppression systems should also be installed in high-risk zones.  

Finally, all electrical equipment should certified for use in combustible dust zones using ATEX standards in Europe and IECEx globally. Equipment must be dust-tight and marked with the appropriate EX symbol. NFPA 499 and NFPA 70 (also known as the National Electrical Code) should be followed to classify areas and select suitable equipment and protection. Surface temperatures also need to remain below the ignition temperature of the dust present, and all equipment should be regularly inspected and maintained to prevent dust ingress and overheating. Faulty equipment should be at once repaired or replaced. 

Operators of bulk cargo warehouses should always conduct a dust hazard analysis when looking at potential new cargoes to know the explosion risks, ignition sources and mitigation strategies

Fire safety systems and planning

Given the increased risk of fires from dust explosions, early suppression fast response (ESFR) sprinklers designed for high-density bulk storage should be considered in all bulk cargo warehouse storage zones. Fire-rated walls and doors should also be considered to separate high-risk areas and prevent fire spread. 

Careful consideration should be given to the selection/specification of the handling equipment used within these operations. Avoiding the temptation to use handling equipment designed and manufactured for other non-hazardous cargoes. 

A fire safety plan tailored to the facility’s layout and hazards should be developed, including evacuation routes and emergency procedures. Regular explosion and fire risk assessments and safety audits should be carried out, updating plans as operations change, and ongoing training for staff should be provided – including on dust hazard awareness and equipment safety.  

Good practice would see response plans for dust explosions and bulk material fires being developed in collaboration with the local fire service and specialists in dust explosion risk. 

Conclusions 

Dust explosion risk in bulk cargo warehouses is real and often underestimated. Rigorous dust control, hazard analysis and use of certified, dust-tight and meticulously maintained equipment are all vital.  

Explosion and fire safety should be a primary consideration in designing the layout and handling methods of bulk cargo warehouses, with a comprehensive array of monitoring, detection and suppression systems installed.  

Regular audits of housekeeping are needed to ensure that dust build-up is minimised and controlled to within acceptable levels for each type of bulk cargo, while safety practices, training and incident analysis should be regularly reviewed to adapt to evolving risks.